In the well completion and production arts, production systems that enable operators to pinpoint fluid placement and volume during openhole fracturing (frac) operations are very desirable. These systems are used to establish openhole isolation between zones, zone lobes, or fault lines, so fracture fluid may be delivered where it is needed, for maximum effect. The systems are designed to incorporate short-radius open-hole packers and frac sleeves to isolate intervals of an underground fluid production section for targeted fracturing treatment placement. The result is greater control of the frac treatment and a greater chance of fracturing the entire length of the lateral and increasing production.
Such systems may be advantageously deployed as a one-trip installation and set in place by the application of hydraulic pressure. Isolation and casing packers may be set against a ball seat in the shoe of the liner. The drill rig can then be moved to another location and the desired frac treatment may be performed by the application of hydraulic pressure by pumping when ready.
Frac treatment is performed by providing fluidic access through openings in the tubular string in a generally radial direction. Such openings allow fluid communication between the ID of the flow channel and an annulus created between the tubular string and a borehole wall (casing or openhole). Openable and closable valves are employed in concert with such openings to selectively promote and prevent the fluid movement noted above.
One frac sleeve arrangement employed in these systems is a slidable frac sleeve. A slidable frac sleeve employs a housing having an opening, a slidable sleeve translatable relative to the housing to either misalign entirely with the opening or to align a port with the opening, and a spring to bias the sleeve to a selected position (open or closed). The sleeve employs a plug valve that is configured to receive a plug to close the valve; the plug valve may include a ball seat in the sleeve that is configured to receive a corresponding ball that is configured to be seated in the ball seat for closing the valve. The systems typically employ a plurality of plug valves that are sized with successively smaller valve openings proceeding inwardly from the surface along the length of the production string.
In use, successively larger plugs (e.g. balls) are dropped into the string, each configured to engage a corresponding valve seat, closing their respective valves and opening the corresponding frac sleeves at various locations along the production string. Desired fracture volumes can be displaced with timing of the ball releases to accurately place frac fluid in each desired interval of the production string.
It has previously been the practice to remove the balls and ball seats in the sleeves after the frac operations. This has included flowing the balls back to the surface by high production rate flows and by drilling out the ball seats to recover a full-open string inside or inner diameter (ID). While effective, such ball removal and drilling operations represent additional drill string operations that require additional equipment and time on the drill rig.
Therefore, it is desirable to provide frac tools that incorporate plug valves, such as ball valves, that may be removed to recover the full ID of the drill string without drilling.